This application claims the benefit of Korean Patent Application Nos. 2002-14201, filed on Mar. 15, 2002, 2002-15436, filed on Mar. 21, 2002, 2002-15449, filed on Mar. 21, 2002, and 2002-15739, filed on Mar. 22, 2002, all of which are hereby incorporated by reference for all purposes as if fully set forth herein. This application incorporates by reference two co-pending applications, Ser. No. 10/184,096, filed on Jun. 28, 2002, entitled xe2x80x9cSYSTEM AND METHOD FOR MANUFACTURING LIQUID CRYSTAL DISPLAY DEVICESxe2x80x9d and Ser. No. 10/184,088, filed on Jun. 28, 2002, entitled xe2x80x9cSYSTEM FOR FABRICATING LIQUID CRYSTAL DISPLAY AND METHOD OF FABRICATING LIQUID CRYSTAL DISPLAY USING THE SAMExe2x80x9d, as if fully set forth herein.
1. Field of the Invention
The present invention relates to a liquid crystal dispensing apparatus, and more particularly, to a liquid crystal dispensing apparatus capable of determining an amount of liquid crystal material to be dispensed onto a substrate and also capable of determining an amount of liquid crystal material remaining within a liquid crystal container.
2. Discussion of the Background Art
As portable electric devices such as mobile phones, personal digital assistants (PDA), notebook computers, etc., continue to be developed, small, light, and power-efficient flat panel display devices such as liquid crystal displays (LCD), plasma display panels (PDP), field emission displays (FED), vacuum fluorescent displays (VFD), etc., have become the subject of intense research. Due to their ability to be mass-produced, ease in driving, and superior image qualities, LCDs are of particular interest.
LCDs display information on a screen using refractive anisotropic properties of liquid crystal material. Referring to FIG. 1, an LCD 1 typically includes a lower substrate (i.e., a driving device array substrate) 5 connected to an upper substrate (i.e., a color filter substrate) 3 via sealant 9. A layer of liquid crystal material 7 separates the lower and upper substrates 5 and 3. A plurality of pixels (not shown) are formed on the lower substrate 5 and driving devices such as thin film transistors (TFTs) are formed on each of the pixels. A color filter layer is formed on the upper substrate 3 allowing the LCD to express color. Further, pixel electrodes and a common electrode are also formed on the lower and upper substrates 5 and 3, respectively. An alignment layer is formed on both the lower and upper substrates 5 and 3 to uniformly align molecules within the layer of liquid crystal material 7. The molecules within the layer of liquid crystal material may be selectively oriented by the driving devices. Accordingly, as the orientation of the molecules within the liquid crystal material is manipulated, the amount of light transmitted through portions of the LCD may be selectively controlled to convey information.
Fabrication processes for LCD devices may be roughly divided into a driving device array fabrication process, where driving devices are formed on the lower substrate 5, a color filter fabrication process, where the color filter is formed on the upper substrate 3, and a cell fabrication process. These fabrication processes will now be described with reference to FIG. 2.
Referring to FIG. 2, in the driving device array substrate fabrication process (S101), a plurality pixel areas are formed at crossings of a plurality of gate lines and data lines formed on the lower substrate 5 and thin film transistors arranged in each pixel area are connected to gate lines and corresponding ones of data lines. Also, pixel electrodes are connected to each of the thin film transistors to drive the layer of liquid crystal material. Accordingly, the layer of liquid crystal material may be driven in accordance with a signal applied to the thin film transistor.
In the color filter fabrication process (S104), red (R), green (G), and blue (B) color filter layers for producing color and a common electrode are formed on the upper substrate 3.
The alignment layer is formed on both the lower and upper substrates 5 and 3, respectively. After being formed on the substrates, the alignment layer is rubbed to induce molecules within the layer of liquid crystal material to inherit a predetermined pretilt angle and alignment direction between the lower and upper substrates 5 and 3 (S102 and S105). Subsequently, spacers are dispensed over the lower substrate 5 to maintain a uniform cell gap between the upper and lower substrates (S103). The sealant is applied to an outer portion of the upper substrate 3 (S106) and the lower substrate 5 is pressed and attached to the upper substrate 3 (S107).
The lower and upper substrates 5 and 3 are formed from glass substrates having an area larger in size than any individual panel areas. Accordingly, a plurality of corresponding panel areas where driving devices and color filter layers are may be arranged within the attached glass substrates. Thus, in fabricating individual liquid crystal display panels, the attached glass substrates are cut into individual panels (S108). Subsequently, liquid crystal material is injected through a liquid crystal injection opening into the cell gap formed between the two substrates of each individual liquid crystal display panel (S109). After the liquid crystal material is injected, the liquid crystal injection opening is sealed (S109) and each individual liquid crystal display panel is inspected (S110).
To inject the liquid crystal material through the liquid crystal injection opening, a pressure difference between the exterior and the interior of the liquid crystal display panel is induced. FIG. 3 illustrates a device used to inject liquid crystal material into cell gaps of liquid crystal display panels.
Referring to FIG. 3, liquid crystal material 14 is provided in a container 12 arranged within a vacuum chamber 10 that is connected to a vacuum pump (not shown) capable of creating and maintaining a vacuum within the vacuum chamber. A liquid crystal display panel moving device (not shown) is installed within the vacuum chamber 10 and moves separated liquid crystal display panels down from an upper portion of the container 12 toward the surface of the liquid crystal material 14. In what is known as a liquid crystal injection method, the liquid crystal injection opening 16 of each liquid crystal display panel is arranged to contact the liquid crystal material. Subsequently, nitrogen gas (N2) is pumped into the vacuum chamber to increase the pressure therein from the initial vacuum pressure. As the pressure within the vacuum chamber 10 increases, the liquid crystal material 14 contacting the liquid crystal injection opening 16 is extruded (i.e., injected) into the cell gap of the liquid crystal display panel due to the pressure difference between the interior of the liquid crystal display panel and the interior of the vacuum chamber containing the pumped nitrogen gas. After the cell gap is completely filled with liquid crystal material 14, the injection opening 16 is sealed using a sealant.
Injecting liquid crystal material according to the process described above is disadvantageous, however, at least for the following reasons.
First, the amount of time required to completely inject liquid crystal material 14 into the liquid crystal display panel 1 can be excessively long. For example, the cell gap between the driving device array and the color filter substrates is very narrow (e.g., on the order of a few micrometers) and, therefore, only a very small amount of liquid crystal material can be injected into the liquid crystal display panel at any time. Accordingly, injecting liquid crystal material into a typical 15-inch liquid crystal display panel using the injection process described above may take up to about eight hours. Thus, the time required to fabricate LCDs is unduly increased with the use of the liquid crystal injection process.
Second, the amount of liquid crystal material required by the liquid crystal injection method described above is exceedingly large. While only a small amount of liquid crystal is removed from the container 12, a large amount of liquid crystal may become exposed to the atmosphere or to the nitrogen gas. Accordingly, a large amount of liquid crystal material reacts with, and can be contaminated by, nitrogen or other gases within the atmosphere. As a result, the cost of fabricating LCDs increases because liquid crystal material not injected into the liquid crystal display panel must be discarded after the injection process.
Accordingly, the present invention is directed to a liquid crystal dispensing apparatus having a confirming function for determining an amount of amount of liquid crystal material remaining within a liquid crystal apparatus and a method of detecting the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An advantage of the present invention provides an apparatus for dispensing liquid crystal material directly onto a glass substrate having an area greater than an area of at least one individual LCD panel.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. These and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there may be provided a liquid crystal dispensing apparatus capable of dispensing liquid crystal material onto a substrate within at least one individual LCD panel area that may, for example, include a needle sheet having a discharging hole through which the liquid crystal may be dispensed onto the substrate, a needle moveable between a down position, where the needle blocks the discharging hole, and an up position, where the needle is separated from the discharging hole, a spring member to bias the needle toward the down position, and a solenoid coil to provide a magnetic force to bias the needle toward the up position, an electric power supply for providing electric power to the solenoid coil, enabling the solenoid coil to bias the needle toward the up position, a gas supply for providing pressurized gas to force liquid crystal material through the discharging hole when the needle is biased in the up position, and a main control unit for determining an amount of liquid crystal material to be dispensed onto the substrate and for determining an amount of liquid crystal material remaining within the liquid crystal dispensing apparatus.
In one aspect of the present invention, the main control unit may determine the amount of liquid crystal material remaining within the liquid crystal dispensing apparatus by deducting a determined total amount of liquid crystal material dispensed from a predetermined amount of liquid crystal contained in the liquid crystal dispensing apparatus.
In another aspect of the present invention, the main control unit may include a unitary amount dispensed determining unit for determining a unitary amount of liquid crystal material that is to be dispensed onto the substrate, a dispensing counter unit for determining the number of times unitary amounts of liquid crystal material have been dispensed by determining the number of times power from the electric power supply is applied to the solenoid coil, a total amount dispensed determining unit for determining a total amount of liquid crystal material that is dispensed onto the substrate based on the unitary amount of liquid crystal material to be dispensed and the number of times unitary amounts of liquid crystal material have been dispensed, and an amount remaining determining unit for determining an amount of liquid crystal material remaining within the liquid crystal dispensing apparatus by deducting the total amount of liquid crystal material that is dispensed onto the substrate from an initial amount of liquid crystal material contained in the liquid crystal dispensing apparatus.
In yet another aspect of the present invention, a method for determining an amount of liquid crystal material remaining within a liquid crystal dispensing apparatus may include the steps of determining a total amount of liquid crystal material dispensed onto a substrate, based on a unitary amount of liquid crystal material to be dispensed and the number of times liquid crystal material is dispensed, and determining an amount of liquid crystal material remaining within the liquid crystal apparatus by deducting the total amount of liquid crystal material dispensed onto the substrate from a predetermined amount of liquid crystal material contained within the liquid crystal dispensing apparatus.
In still another aspect of the present invention, if it is determined that an amount of liquid crystal material remaining within the liquid crystal dispensing apparatus is less than a predetermined minimum threshold amount, a signal may be generated representing an instruction to fill the liquid crystal dispensing apparatus with liquid crystal material. Alternatively, if it is determined that an amount of liquid crystal material remaining is greater than the predetermined minimum threshold amount and the liquid crystal material has been dispensed onto a predetermined number of substrates, a signal may be transmitted representing an instruction to dispense the liquid crystal material remaining within the liquid crystal dispensing apparatus onto an additional substrate.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there may also be provided a liquid crystal dispensing apparatus including a transparent liquid crystal container for containing liquid crystal material that is to be dispensed onto a substrate, wherein the liquid crystal container is supplied with pressurized gas, a nozzle arranged at a lower portion of the liquid crystal container, through which liquid crystal material is dispensed, and a valve structure for allowing liquid crystal material within the liquid crystal container to enter the nozzle via pressure from the supplied gas.
In one aspect of the present invention, the valve structure may include a needle sheet having a discharging hole through which liquid crystal material may be discharged from the liquid crystal container to the nozzle, a needle member arranged within the liquid crystal container and capable of moving toward and away from the needle sheet, wherein liquid crystal material may be prevented from entering the discharging hole when the needle member contacts the needle sheet, and a solenoid provided for moving the needle member away from the needle sheet, thereby allowing liquid crystal material to enter into the discharging hole.
In another aspect of the present invention, the nozzle may include a discharging opening through which liquid crystal material may be dispensed, and a supporting portion for fixing the discharging opening. In another aspect of the present invention, the liquid crystal container may be made of a material such as quartz.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there may also be provided a liquid crystal dispensing apparatus including a liquid crystal container filled with liquid crystal material to be dispensed on a substrate, wherein the liquid crystal container is supplied with pressurized gas, a transparent tube arranged adjacent the liquid crystal container and filled with the liquid crystal material contained by the liquid crystal container, a nozzle arranged at a lower portion of the liquid crystal container, through which liquid crystal material may be dispensed, and a valve structure for providing liquid crystal material from the liquid crystal container to the nozzle via pressure from the supplied gas.
In one aspect of the present invention, the liquid crystal container may be formed of an opaque material such as stainless steel and the tube may be provided as a transparent pipe made of a material such as quartz coated with and fluorine resin, wherein liquid crystal material within the liquid crystal container is also contained within the tube, and wherein the tube measures an amount of liquid crystal material remaining in the liquid crystal container.
In another aspect of the present invention, there may also be provided a liquid crystal dispensing apparatus including, for example, a liquid crystal dispensing unit in which liquid crystal is contained for directly dispensing liquid crystal material onto a substrate, and a weight measuring unit arranged within the liquid crystal dispensing unit for measuring a weight of the liquid crystal material remaining within the liquid crystal dispensing unit.
In one aspect of the present invention, the liquid crystal dispensing unit may include a liquid crystal container filled with liquid crystal to be dispensed onto a substrate, wherein the liquid crystal container is supplied with gas, an upper cap for fixing to the liquid crystal container, a nozzle arranged at a lower portion of the liquid crystal container through which liquid crystal material may be dispensed onto a substrate, and a valve structure for providing liquid crystal material from the liquid crystal container to the nozzle via pressure from the supplied gas.
In another aspect of the present invention, the weight measuring unit may be provided as a scale and arranged between a lower surface of the upper cap an upper surface of a fixing member such that a weight of the liquid crystal dispensing unit is applied to the scale and an amount of liquid crystal material remaining within the liquid crystal dispensing unit may be determined. The weight of the remaining amount of liquid crystal material may be converted into a volume and displayed through a display unit.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.